The sweetener industry employs wood-based carbon as an adsorber and filter medium for processes such as deashing and decolorization. When wood-based carbon is regenerated in the presence of steam, volatile phosphorus is released. This phosphorus, in elemental form or in the form of phosphates, is known to cause severe deterioration of the insulation in regeneration furnaces, the tubes of waste heat boilers, and parts of other regeneration equipment.
It would therefore be beneficial to have an analytical procedure to monitor volatile phosphorus released from wood-based carbon at regeneration conditions and such method should not require total phosphorus analysis. The desired method for determining the amount of volatile phosphorus in a carbon sample should be easy to perform and highly accurate.
Various methods for determining phosphorus content are known in the prior art. U.S. Pat. No. 4,599,316 to Hahn et al discloses a spectrophotometric method for determining the concentration of inorganic phosphate in a sample fluid, such as bodily fluids. An ammonium molybdate reagent is employed as a complexing agent.
In U.S. Pat. No. 3,796,543 to Kamphake, a continuous automatic system is employed for measuring the amount of phosphates in aqueous fluids, e.g., sewage effluent. This analytical technique is based on what is known as the molybdenum blue reaction.
U.S. Pat. No. 4,533,639 to Kojima et al discloses a colorimetric analytical method for determining the amount of phosphate in a phosphate-containing coating stripped from a ferrous metal surface.
U.S. Patent No. 3,425,805 to Grobin, Jr. discloses a colorimetric method for determining the phosphite content of electroless plating baths. A molybdate ion complex is formed in solution with the phosphite ions.
None of the above-mentioned analytical methods, however, are directed to problems associated with carbon used as a sorbent generally, and in particular, determining the volatile phosphorus content of solids such as carbon. Thus, there is still a present need for an accurate and efficient analytical technique for such phosphorus determinations.